This invention relates to a wafer inspecting system, more particularly it relates to a wafer inspecting system for inspecting electric characteristics of circuit patterns formed on a semiconductor wafer.
2. Description of the Related Art
As for a semiconductor wafer, a multiplicity of same circuit patterns are formed on the surface thereof. Each circuit pattern is judged whether it is good or bad for inspecting the electric characteristics of each circuit pattern before the wafer is separated into individual dies.
Said wafer inspecting system is composed of a cassette stocking part, a wafer conveying part, a wafer table, a control part and the like. A cassette storing a multiplicity of wafers to be inspected is attached to the cassette stocking part 4, and the wafers are taken out from the cassette one by one so as to be conveyed to the wafer table by the wafer conveying part. The wafer table holds the wafer, and moves horizontally in the direction of X-Y and vertically in the direction of Z according to the element array during the element inspection.
The control part consists of a probe stage, a tester and the like. A probe card adapting to the wafer to be inspected is mounted to the probe stage and each electrode pad of the circuit is touched to a probe needle provided in the probe card whereby the electric characteristics of each circuit pattern is inspected with the tester one after another.
Further, the wafer that has been inspected is conveyed from the wafer table to the cassette by the wafer conveying part and is stored in the former shelf of the cassette.
However, the conventional wafer inspecting system has a disadvantage in that the inspecting time for one cassette becomes longer because a multiplicity of wafers stored in a cassette are processed with only one wafer prober.
Moreover, as shown in Japan Patent Application Laid-Open No. 62-86835, there is another wafer inspecting system provided with two wafer probing stages and a conveying device for wafer cassettes, wherein a wafer is taken out from the wafer cassette conveyed by the conveying device and then is inspected at the probing stage. This wafer inspecting system can shorten to 1/2 of the inspecting time for one cassette, however, has the disadvantage in that when there is something wrong with the conveying device, so that the wafer is stopped being conveyed to the probing stage, therefore, the inspection is not performed efficiently and the inspecting time for one cassette becomes longer.